Encoder, a decoder and corresponding methods for local illumination compensation

ABSTRACT

An apparatus and method for inter prediction of a block includes estimating local illumination compensation (LIC) parameters using first reference samples of a current block and second reference samples of a reference block, wherein a third reference sample of the second reference samples is based on an integer part of a fractional motion vector (MV), and obtaining inter prediction of the current block according to the LIC parameters.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/RU2020/050003 filed on Jan. 16, 2020, which claims the benefitof U.S. Provisional Application No. 62/793,351 filed on Jan. 16, 2019.The disclosures of the aforementioned applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field ofpicture processing and in particularly to local illuminationcompensation (LIC) based on integer pixel (pel) motion compensation.

BACKGROUND

Video coding (i.e., video encoding and decoding) is used in a wide rangeof digital video applications, for example broadcast digital television(TV), video transmission over internet and mobile networks, real-timeconversational applications such as video chat, video conferencing,DIGITAL VERSATILE DISC (DVD) and BLU-RAY DISCS, video contentacquisition and editing systems, and camcorders of securityapplications.

The amount of video data needed to depict even a relatively short videocan be substantial, which may result in difficulties when the data is tobe streamed or otherwise communicated across a communications networkwith limited bandwidth capacity. Thus, video data is generallycompressed before being communicated across modern daytelecommunications networks. The size of a video could also be an issuewhen the video is stored on a storage device because memory resourcesmay be limited. Video compression devices often use software and/orhardware at the source to code the video data prior to transmission orstorage, thereby decreasing the quantity of data needed to representdigital video images. The compressed data is then received at thedestination by a video decompression device that decodes the video data.With limited network resources and ever increasing demands of highervideo quality, improved compression and decompression techniques thatimprove compression ratio with little to no sacrifice in picture qualityare desirable.

SUMMARY

Embodiments of the present application provide apparatuses and methodsfor encoding and decoding according to the independent claims.

The foregoing and other objects are achieved by the subject matter ofthe independent claims. Further implementation forms are apparent fromthe dependent claims, the description and the figures.

According to a first aspect, embodiment of the disclosure relates to acoding method, wherein the coding includes decoding or encoding, themethod includes estimating LIC parameters by using reference samples ofa current block and reference samples of a reference block, wherein atleast one of the reference samples of the reference block is obtained byusing an integer part of a fractional motion vector (MV), and obtaininginter prediction of the current block according to the LIC parameters.

The method according to the first aspect of the disclosure can beperformed by the apparatus according to the second aspect of thedisclosure. The apparatus according to the second aspect of thedisclosure includes an obtaining unit configured to obtain referencesamples of a reference block, wherein at least one of the referencesamples of the reference block is obtained by using the integer part ofa fractional MV, and an estimating unit configured to estimate LICparameters by using reference samples of a current block and thereference samples of the reference block.

The obtaining unit, further configured to obtain inter prediction of thecurrent block according to the LIC parameters.

Further features and implementation forms of the method according to thefirst aspect of the disclosure correspond to the features andimplementation forms of the apparatus according to the second aspect ofthe disclosure.

According to a third aspect, embodiment the disclosure relates to anapparatus for decoding a video stream includes a processor and a memory.The memory is storing instructions that cause the processor to performthe method according to the first aspect.

According to a forth aspect, embodiment of the disclosure relates to anapparatus for encoding a video stream includes a processor and a memory.The memory is storing instructions that cause the processor to performthe method according to the first aspect.

According to a fifth aspect, a computer-readable storage medium havingstored thereon instructions that when executed cause one or moreprocessors configured to code video data is proposed. The instructionscause the one or more processors to perform a method according to thefirst or second aspect or any possible embodiment of the first aspect.

According to a sixth aspect, embodiment of the disclosure relates to acomputer program comprising program code for performing the methodaccording to the first aspect or any possible embodiment of the firstaspect when executed on a computer.

According to embodiments of the disclosure, at least one of thereference samples of the reference block is obtained by using theinteger part of a fractional MV. This scheme allows reduce the latencyby dropping one stage. Therefore, it is a simplification for interprediction of the current block when reference samples of referenceblock include the fractional MV.

Details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following embodiments of the disclosure are described in moredetail with reference to the attached figures and drawings.

FIG. 1A is a block diagram showing an example of a video coding systemconfigured to implement embodiments of the disclosure;

FIG. 1B is a block diagram showing another example of a video codingsystem configured to implement embodiments of the disclosure;

FIG. 2 is a block diagram showing an example of a video encoderconfigured to implement embodiments of the disclosure;

FIG. 3 is a block diagram showing an example structure of a videodecoder configured to implement embodiments of the disclosure;

FIG. 4 is a figure illustrating neighboring samples used for deriving ICparameters;

FIG. 5 is a block diagram illustrating an example of an encodingapparatus or a decoding apparatus;

FIG. 6 is a block diagram illustrating another example of an encodingapparatus or a decoding apparatus;

FIG. 7A is a figure with a proposed design of a pipeline with LIC;

FIG. 7B is an exemplary figure with LIC based on integer pel motioncompensation;

FIG. 8 is a flowchart illustrating exemplary inter prediction of acurrent block by applying LIC;

FIG. 9 is a block diagram showing an example structure of an apparatusfor inter prediction of a current block by applying LIC;

FIG. 10 is a block diagram showing an example structure of a contentsupply system 3100 which realizes a content delivery service; and

FIG. 11 is a block diagram showing a structure of an example of aterminal device.

In the following identical reference signs refer to identical or atleast functionally equivalent features if not explicitly specifiedotherwise.

DESCRIPTION OF THE EMBODIMENTS

In the following description, reference is made to the accompanyingfigures, which form part of the disclosure, and which show, by way ofillustration, specific aspects of embodiments of the disclosure orspecific aspects in which embodiments of the present disclosure may beused. It is understood that embodiments of the disclosure may be used inother aspects and comprise structural or logical changes not depicted inthe figures. The following detailed description, therefore, is not to betaken in a limiting sense.

For instance, it is understood that a disclosure in connection with adescribed method may also hold true for a corresponding device or systemconfigured to perform the method and vice versa. For example, if one ora plurality of specific method steps are described, a correspondingdevice may include one or a plurality of units, e.g. functional units,to perform the described one or plurality of method steps (e.g. one unitperforming the one or plurality of steps, or a plurality of units eachperforming one or more of the plurality of steps), even if such one ormore units are not explicitly described or illustrated in the figures.On the other hand, for example, if a specific apparatus is describedbased on one or a plurality of units, e.g. functional units, acorresponding method may include one step to perform the functionalityof the one or plurality of units (e.g. one step performing thefunctionality of the one or plurality of units, or a plurality of stepseach performing the functionality of one or more of the plurality ofunits), even if such one or plurality of steps are not explicitlydescribed or illustrated in the figures. Further, it is understood thatthe features of the various exemplary embodiments and/or aspectsdescribed herein may be combined with each other, unless further notedotherwise.

Video coding typically refers to the processing of a sequence ofpictures, which form the video or video sequence. Instead of the term“picture” the term “frame” or “image” may be used as synonyms in thefield of video coding. Video coding (or coding in general) comprises twoparts video encoding and video decoding. Video encoding is performed atthe source side, typically comprising processing (e.g. by compression)the original video pictures to reduce the amount of data required forrepresenting the video pictures (for more efficient storage and/ortransmission). Video decoding is performed at the destination side andtypically comprises the inverse processing compared to the encoder toreconstruct the video pictures. Embodiments referring to “coding” ofvideo pictures (or pictures in general) shall be understood to relate to“encoding” or “decoding” of video pictures or respective videosequences. The combination of the encoding part and the decoding part isalso referred to as coding and decoding (CODEC).

In case of lossless video coding, the original video pictures can bereconstructed, i.e. the reconstructed video pictures have the samequality as the original video pictures (assuming no transmission loss orother data loss during storage or transmission). In case of lossy videocoding, further compression, e.g. by quantization, is performed, toreduce the amount of data representing the video pictures, which cannotbe completely reconstructed at the decoder, i.e. the quality of thereconstructed video pictures is lower or worse compared to the qualityof the original video pictures.

Several video coding standards belong to the group of “lossy hybridvideo codecs” (i.e. combine spatial and temporal prediction in thesample domain and two-dimensional (2D) transform coding for applyingquantization in the transform domain). Each picture of a video sequenceis typically partitioned into a set of non-overlapping blocks and thecoding is typically performed on a block level. In other words, at theencoder the video is typically processed, i.e. encoded, on a block(video block) level, e.g. by using spatial (intra picture) predictionand/or temporal (inter picture) prediction to generate a predictionblock, subtracting the prediction block from the current block (blockcurrently processed/to be processed) to obtain a residual block,transforming the residual block and quantizing the residual block in thetransform domain to reduce the amount of data to be transmitted(compression), whereas at the decoder the inverse processing compared tothe encoder is applied to the encoded or compressed block to reconstructthe current block for representation. Furthermore, the encoderduplicates the decoder processing loop such that both will generateidentical predictions (e.g. intra- and inter predictions) and/orre-constructions for processing, i.e. coding, the subsequent blocks.

In the following embodiments of a video coding system 10, a videoencoder 20 and a video decoder 30 are described based on FIGS. 1 to 3 .

FIG. 1A is a schematic block diagram illustrating an example codingsystem 10, e.g. a video coding system 10 (or short coding system 10)that may utilize techniques of this present application. Video encoder20 (or short encoder 20) and video decoder 30 (or short decoder 30) ofvideo coding system 10 represent examples of devices that may beconfigured to perform techniques in accordance with various examplesdescribed in the present application.

As shown in FIG. 1A, the coding system 10 comprises a source device 12configured to provide encoded picture data 21 e.g. to a destinationdevice 14 for decoding the encoded picture data 21.

The source device 12 comprises an encoder 20, and may additionally, i.e.optionally, comprise a picture source 16, a pre-processor (orpre-processing unit) 18, e.g. a picture pre-processor 18, and acommunication interface or communication unit 22.

The picture source 16 may comprise or be any kind of picture capturingdevice, for example a camera for capturing a real-world picture, and/orany kind of a picture generating device, for example a computer-graphicsprocessor for generating a computer animated picture, or any kind ofother device for obtaining and/or providing a real-world picture, acomputer generated picture (e.g. a screen content, a virtual reality(VR) picture) and/or any combination thereof (e.g. an augmented reality(AR) picture). The picture source may be any kind of memory or storagestoring any of the aforementioned pictures.

In distinction to the pre-processor 18 and the processing performed bythe pre-processing unit 18, the picture or picture data 17 may also bereferred to as raw picture or raw picture data 17.

Pre-processor 18 is configured to receive the (raw) picture data 17 andto perform pre-processing on the picture data 17 to obtain apre-processed picture 19 or pre-processed picture data 19.Pre-processing performed by the pre-processor 18 may, e.g., comprisetrimming, color format conversion (e.g. from red, green, and blue (RGB)to luminance, chroma blue-difference, and chroma red-difference(YCbCr)), color correction, or de-noising. It can be understood that thepre-processing unit 18 may be optional component.

The video encoder 20 is configured to receive the pre-processed picturedata 19 and provide encoded picture data 21 (further details will bedescribed below, e.g., based on FIG. 2 ).

Communication interface 22 of the source device 12 may be configured toreceive the encoded picture data 21 and to transmit the encoded picturedata 21 (or any further processed version thereof) over communicationchannel 13 to another device, e.g. the destination device 14 or anyother device, for storage or direct reconstruction.

The destination device 14 comprises a decoder 30 (e.g. a video decoder30), and may additionally, i.e. optionally, comprise a communicationinterface or communication unit 28, a post-processor 32 (orpost-processing unit 32) and a display device 34.

The communication interface 28 of the destination device 14 isconfigured receive the encoded picture data 21 (or any further processedversion thereof), e.g. directly from the source device 12 or from anyother source, e.g. a storage device, e.g. an encoded picture datastorage device, and provide the encoded picture data 21 to the decoder30.

The communication interface 22 and the communication interface 28 may beconfigured to transmit or receive the encoded picture data 21 or encodeddata 13 via a direct communication link between the source device 12 andthe destination device 14, e.g. a direct wired or wireless connection,or via any kind of network, e.g. a wired or wireless network or anycombination thereof, or any kind of private and public network, or anykind of combination thereof.

The communication interface 22 may be configured to package the encodedpicture data 21 into an appropriate format, e.g. packets, and/or processthe encoded picture data using any kind of transmission encoding orprocessing for transmission over a communication link or communicationnetwork.

The communication interface 28, forming the counterpart of thecommunication interface 22, may be, e.g. configured to receive thetransmitted data and process the transmission data using any kind ofcorresponding transmission decoding or processing and/or de-packaging toobtain the encoded picture data 21.

Both, communication interface 22 and communication interface 28 may beconfigured as unidirectional communication interfaces as indicated bythe arrow for the communication channel 13 in FIG. 1A pointing from thesource device 12 to the destination device 14, or bi-directionalcommunication interfaces, and may be configured, e.g. to send andreceive messages, e.g. to set up a connection, to acknowledge andexchange any other information related to the communication link and/ordata transmission, e.g. encoded picture data transmission.

The decoder 30 is configured to receive the encoded picture data 21 andprovide decoded picture data 31 or a decoded picture 31 (further detailswill be described below, e.g., based on FIG. 3 or FIG. 5 ).

The post-processor 32 of destination device 14 is configured topost-process the decoded picture data 31 (also called reconstructedpicture data), e.g. the decoded picture 31, to obtain post-processedpicture data 33, e.g. a post-processed picture 33. The post-processingperformed by the post-processing unit 32 may comprise, e.g. color formatconversion (e.g. from YCbCr to RGB), color correction, trimming, orre-sampling, or any other processing, e.g. for preparing the decodedpicture data 31 for display, e.g. by display device 34.

The display device 34 of the destination device 14 is configured toreceive the post-processed picture data 33 for displaying the picture,e.g. to a user or viewer. The display device 34 may be or comprise anykind of display for representing the reconstructed picture, e.g. anintegrated or external display or monitor. The displays may, e.g.comprise liquid-crystal displays (LCDs), organic light-emitting diodes(LEDs) (OLEDs) displays, plasma displays, projectors, micro LEDdisplays, liquid-crystal on silicon (LCoS), digital light processor(DLP) or any kind of other display.

Although FIG. 1A depicts the source device 12 and the destination device14 as separate devices, embodiments of devices may also comprise both orboth functionalities, the source device 12 or correspondingfunctionality and the destination device 14 or correspondingfunctionality. In such embodiments the source device 12 or correspondingfunctionality and the destination device 14 or correspondingfunctionality may be implemented using the same hardware and/or softwareor by separate hardware and/or software or any combination thereof.

As will be apparent for the skilled person based on the description, theexistence and (exact) split of functionalities of the different units orfunctionalities within the source device 12 and/or destination device 14as shown in FIG. 1A may vary depending on the actual device andapplication.

The encoder 20 (e.g. a video encoder 20) or the decoder 30 (e.g. a videodecoder 30) or both encoder 20 and decoder 30 may be implemented viaprocessing circuitry as shown in FIG. 1B, such as one or moremicroprocessors, digital signal processors (DSPs), application-specificintegrated circuits (ASICs), field-programmable gate arrays (FPGAs),discrete logic, hardware, video coding dedicated or any combinationsthereof. The encoder 20 may be implemented via processing circuitry 46to embody the various modules as discussed with respect to encoder 20 ofFIG. 2 and/or any other encoder system or subsystem described herein.The decoder 30 may be implemented via processing circuitry 46 to embodythe various modules as discussed with respect to decoder 30 of FIG. 3and/or any other decoder system or subsystem described herein. Theprocessing circuitry may be configured to perform the various operationsas discussed later. As shown in FIG. 5 , if the techniques areimplemented partially in software, a device may store instructions forthe software in a suitable, non-transitory computer-readable storagemedium and may execute the instructions in hardware using one or moreprocessors to perform the techniques of this disclosure. Either of videoencoder 20 and video decoder 30 may be integrated as part of a CODEC ina single device, for example, as shown in FIG. 1B.

Source device 12 and destination device 14 may comprise any of a widerange of devices, including any kind of handheld or stationary devices,e.g. notebook or laptop computers, mobile phones, smart phones, tabletsor tablet computers, cameras, desktop computers, set-top boxes,televisions, display devices, digital media players, video gamingconsoles, video streaming devices (such as content services servers orcontent delivery servers), broadcast receiver device, broadcasttransmitter device, or the like and may use no or any kind of operatingsystem. In some cases, the source device 12 and the destination device14 may be equipped for wireless communication. Thus, the source device12 and the destination device 14 may be wireless communication devices.

In some cases, video coding system 10 illustrated in FIG. 1A is merelyan example and the techniques of the present application may apply tovideo coding settings (e.g., video encoding or video decoding) that donot necessarily include any data communication between the encoding anddecoding devices. In other examples, data is retrieved from a localmemory, streamed over a network, or the like. A video encoding devicemay encode and store data to memory, and/or a video decoding device mayretrieve and decode data from memory. In some examples, the encoding anddecoding is performed by devices that do not communicate with oneanother, but simply encode data to memory and/or retrieve and decodedata from memory.

For convenience of description, embodiments of the disclosure aredescribed herein, for example, by reference to High-Efficiency VideoCoding (HEVC) or to the reference software of Versatile Video coding(VVC), the next generation video coding standard developed by the JointCollaboration Team on Video Coding (JCT-VC) of InternationalTelecommunication Union (ITU) Telecommunication Standardization Sector(ITU-T) Video Coding Experts Group (VCEG) and International Organizationfor Standardization (ISO)/International Electrotechnical Commission(IEC) Motion Picture Experts Group (MPEG). One of ordinary skill in theart will understand that embodiments of the disclosure are not limitedto HEVC or VVC.

Encoder and Encoding Method:

FIG. 2 shows a schematic block diagram of an example video encoder 20that is configured to implement the techniques of the presentapplication. In the example of FIG. 2 , the video encoder 20 comprisesan input 201 (or input interface 201), a residual calculation unit 204,a transform processing unit 206, a quantization unit 208, an inversequantization unit 210, and inverse transform processing unit 212, areconstruction unit 214, a loop filter unit 220, a decoded picturebuffer (DPB) 230, a mode selection unit 260, an entropy encoding unit270 and an output 272 (or output interface 272). The mode selection unit260 may include an inter prediction unit 244, an intra prediction unit254 and a partitioning unit 262. Inter prediction unit 244 may include amotion estimation unit and a motion compensation unit (not shown). Avideo encoder 20 as shown in FIG. 2 may also be referred to as hybridvideo encoder or a video encoder according to a hybrid video codec.

The residual calculation unit 204, the transform processing unit 206,the quantization unit 208, the mode selection unit 260 may be referredto as forming a forward signal path of the encoder 20, whereas theinverse quantization unit 210, the inverse transform processing unit212, the reconstruction unit 214, the buffer 216, the loop filter 220,the DPB 230, the inter prediction unit 244 and the intra-prediction unit254 may be referred to as forming a backward signal path of the videoencoder 20, wherein the backward signal path of the video encoder 20corresponds to the signal path of the decoder (see video decoder 30 inFIG. 3 ). The inverse quantization unit 210, the inverse transformprocessing unit 212, the reconstruction unit 214, the loop filter 220,the DPB 230, the inter prediction unit 244 and the intra-prediction unit254 are also referred to forming the “built-in decoder” of video encoder20.

Multi-Hypothesis Prediction for Intra and Inter Mode:

Multi-hypothesis prediction is applied to improve intra mode,multi-hypothesis prediction combines one intra prediction and one mergeindexed inter prediction. In a merge coding unit (CU), one flag issignaled for merge mode to select an inter mode from an inter candidatelist when the flag is true. For luma component, the intra candidate listis derived from 4 intra prediction modes including direct current (DC),planar, horizontal, and vertical modes, and the size of the intracandidate list can be 3 or 4 depending on the block shape. When the CUwidth is larger than the double of CU height, horizontal mode isexclusive of the intra mode list and when the CU height is larger thanthe double of CU width, vertical mode is removed from the intra modelist. One intra prediction mode selected by the intra mode index and onemerge indexed prediction selected by the merge index are combined usingweighted average. For chroma component, direct mode (DM) is alwaysapplied without extra signaling. The weights for combining predictionsare described as follow. When DC or planar mode is selected or a codingblock (CB) width or height is smaller than 4, equal weights are applied.For those CBs with CB width and height larger than or equal to 4, whenhorizontal/vertical mode is selected, one CB is firstvertically/horizontally split into four equal-area regions. Each weightset, denoted as (w_intrai, w_interi), where i is from 1 to 4 and(w_intra1, w_inter1)=(6, 2), (w_intra2, w_inter2)=(5, 3), (w_intra3,w_inter3)=(3, 5), and (w_intra4, w_inter4)=(2, 6), will be applied to acorresponding region. (w_intra1, w_inter1) is for the region closest tothe reference samples and (w_intra4, w_inter4) is for the regionfarthest away from the reference samples. Then, the combined predictioncan be calculated by summing up the two weighted predictions andright-shifting 3 bits. Moreover, the intra prediction mode for the intrahypothesis of predictors can be saved for reference of the followingneighboring CUs.

LIC:

LIC is based on a linear model for illumination changes, using a scalingfactor a and an offset b. And it is enabled or disabled adaptively foreach inter-mode coded CU. When LIC applies for a CU, a least squareerror method is employed to derive the parameters a and b by using theneighboring samples of the current CU and their corresponding referencesamples. Furthermore, as illustrated in FIG. 4 , the subsampled (2:1subsampling) neighboring samples of the CU and the corresponding samples(identified by motion information of the current CU or sub-CU) in thereference picture are used. The IC parameters are derived and appliedfor each prediction direction separately.

When a CU is coded with merge mode, the LIC flag is copied fromneighboring blocks, in a way similar to motion information copy in mergemode, otherwise, an LIC flag is signaled for the CU to indicate whetherLIC applies or not.

When LIC is enabled for a picture, additional CU level rate distortion(RD) check is needed to determine whether LIC is applied or not for aCU. When LIC is enabled for a CU, mean-removed sum of absolutedifference (MR-SAD) and mean-removed sum of absoluteHadamard-transformed difference (MR-SATD) are used, instead of SAD andSATD, for integer pel motion search and fractional pel motion search,respectively.

Pictures & Picture Partitioning (Pictures & Blocks):

The encoder 20 may be configured to receive, e.g. via input 201, apicture 17 (or picture data 17), e.g. picture of a sequence of picturesforming a video or video sequence. The received picture or picture datamay also be a pre-processed picture 19 (or pre-processed picture data19). For sake of simplicity the following description refers to thepicture 17. The picture 17 may also be referred to as current picture orpicture to be coded (in particular in video coding to distinguish thecurrent picture from other pictures, e.g. previously encoded and/ordecoded pictures of the same video sequence, i.e. the video sequencewhich also comprises the current picture).

A (digital) picture is or can be regarded as a two-dimensional array ormatrix of samples with intensity values. A sample in the array may alsobe referred to as pixel (picture element) or a pel. The number ofsamples in horizontal and vertical direction (or axis) of the array orpicture define the size and/or resolution of the picture. Forrepresentation of color, typically three-color components are employed,i.e. the picture may be represented or include three sample arrays. InRBG format or color space a picture comprises a corresponding red, greenand blue sample array. However, in video coding each pixel is typicallyrepresented in a luminance and chrominance format or color space, e.g.YCbCr, which comprises a luminance component indicated by Y (sometimesalso L is used instead) and two chrominance components indicated by Cband Cr. The luminance (or luma) component Y represents the brightness orgrey level intensity (e.g. like in a grey-scale picture), while the twochrominance (or chroma) components Cb and Cr represent the chromaticityor color information components. Accordingly, a picture in YCbCr formatcomprises a luminance sample array of luminance sample values (Y), andtwo chrominance sample arrays of chrominance values (Cb and Cr).Pictures in RGB format may be converted or transformed into YCbCr formatand vice versa, the process is also known as color transformation orconversion. If a picture is monochrome, the picture may comprise only aluminance sample array. Accordingly, a picture may be, for example, anarray of luma samples in monochrome format or an array of luma samplesand two corresponding arrays of chroma samples in 4:2:0, 4:2:2, and4:4:4 colour format.

Embodiments of the video encoder 20 may comprise a picture partitioningunit (not depicted in FIG. 2 ) configured to partition the picture 17into a plurality of (typically non-overlapping) picture blocks 203.These blocks may also be referred to as root blocks, macro blocks(H.264/Advanced Video Coding (AVC)) or coding tree blocks (CTBs) orcoding tree units (CTUs) (H.265/HEVC and VVC). The picture partitioningunit may be configured to use the same block size for all pictures of avideo sequence and the corresponding grid defining the block size, or tochange the block size between pictures or subsets or groups of pictures,and partition each picture into the corresponding blocks.

In further embodiments, the video encoder may be configured to receivedirectly a block 203 of the picture 17, e.g. one, several or all blocksforming the picture 17. The picture block 203 may also be referred to ascurrent picture block or picture block to be coded.

Like the picture 17, the picture block 203 again is or can be regardedas a two-dimensional array or matrix of samples with intensity values(sample values), although of smaller dimension than the picture 17. Inother words, the block 203 may comprise, e.g., one sample array (e.g. aluma array in case of a monochrome picture 17, or a luma or chroma arrayin case of a color picture) or three sample arrays (e.g. a luma and twochroma arrays in case of a color picture 17) or any other number and/orkind of arrays depending on the color format applied. The number ofsamples in horizontal and vertical direction (or axis) of the block 203define the size of block 203. Accordingly, a block may, for example, anM×N (M-column by N-row) array of samples, or an M×N array of transformcoefficients.

Embodiments of the video encoder 20 as shown in FIG. 2 may be configuredto encode the picture 17 block by block, e.g. the encoding andprediction is performed per block 203.

Embodiments of the video encoder 20 as shown in FIG. 2 may be furtherconfigured to partition and/or encode the picture by using slices (orvideo slices), wherein a picture may be partitioned into or encodedusing one or more slices (typically non-overlapping), and each slice maycomprise one or more blocks (e.g. CTUs).

Embodiments of the video encoder 20 as shown in FIG. 2 may be furtherconfigured to partition and/or encode the picture by using tile groups(or video tile groups) and/or tiles (or video tiles), wherein a picturemay be partitioned into or encoded using one or more tile groups(typically non-overlapping), and each tile group may comprise, e.g. oneor more blocks (e.g. CTUs) or one or more tiles, wherein each tile, e.g.may be of rectangular shape and may comprise one or more blocks (e.g.CTUs), e.g. complete or fractional blocks.

Residual Calculation:

The residual calculation unit 204 may be configured to calculate aresidual block 205 (or residual 205) based on the picture block 203 anda prediction block 265 (further details about the prediction block 265are provided later), e.g. by subtracting sample values of the predictionblock 265 from sample values of the picture block 203, sample by sample(pixel by pixel) to obtain the residual block 205 in the sample domain.

Transform:

The transform processing unit 206 may be configured to apply atransform, e.g. a discrete cosine transform (DCT) or discrete sinetransform (DST), on the sample values of the residual block 205 toobtain transform coefficients 207 in a transform domain. The transformcoefficients 207 may also be referred to as transform residualcoefficients and represent the residual block 205 in the transformdomain.

The transform processing unit 206 may be configured to apply integerapproximations of DCT/DST, such as the transforms specified forH.265/HEVC. Compared to an orthogonal DCT transform, such integerapproximations are typically scaled by a certain factor. In order topreserve the norm of the residual block which is processed by forwardand inverse transforms, additional scaling factors are applied as partof the transform process. The scaling factors are typically chosen basedon certain constraints like scaling factors being a power of two forshift operations, bit depth of the transform coefficients, tradeoffbetween accuracy and implementation costs, etc. Specific scaling factorsare, for example, specified for the inverse transform, e.g. by inversetransform processing unit 212 (and the corresponding inverse transform,e.g. by inverse transform processing unit 312 at video decoder 30) andcorresponding scaling factors for the forward transform, e.g. bytransform processing unit 206, at an encoder 20 may be specifiedaccordingly.

Embodiments of the video encoder 20 (respectively transform processingunit 206) may be configured to output transform parameters, e.g. a typeof transform or transforms, e.g. directly or encoded or compressed viathe entropy encoding unit 270, so that, e.g., the video decoder 30 mayreceive and use the transform parameters for decoding.

Quantization:

The quantization unit 208 may be configured to quantize the transformcoefficients 207 to obtain quantized coefficients 209, e.g. by applyingscalar quantization or vector quantization. The quantized coefficients209 may also be referred to as quantized transform coefficients 209 orquantized residual coefficients 209.

The quantization process may reduce the bit depth associated with someor all of the transform coefficients 207. For example, an n-bittransform coefficient may be rounded down to an m-bit Transformcoefficient during quantization, where n is greater than m. The degreeof quantization may be modified by adjusting a quantization parameter(QP). For example, for scalar quantization, different scaling may beapplied to achieve finer or coarser quantization. Smaller quantizationstep sizes correspond to finer quantization, whereas larger quantizationstep sizes correspond to coarser quantization. The applicablequantization step size may be indicated by a QP. The QP may for examplebe an index to a predefined set of applicable quantization step sizes.For example, small QPs may correspond to fine quantization (smallquantization step sizes) and large QPs may correspond to coarsequantization (large quantization step sizes) or vice versa. Thequantization may include division by a quantization step size and acorresponding and/or the inverse dequantization, e.g. by inversequantization unit 210, may include multiplication by the quantizationstep size. Embodiments according to some standards, e.g. HEVC, may beconfigured to use a QP to determine the quantization step size.Generally, the quantization step size may be calculated based on a QPusing a fixed point approximation of an equation including division.Additional scaling factors may be introduced for quantization anddequantization to restore the norm of the residual block, which mightget modified because of the scaling used in the fixed pointapproximation of the equation for quantization step size and QP. In oneexample implementation, the scaling of the inverse transform anddequantization might be combined. Alternatively, customized quantizationtables may be used and signaled from an encoder to a decoder, e.g. in abitstream. The quantization is a lossy operation, wherein the lossincreases with increasing quantization step sizes.

Embodiments of the video encoder 20 (respectively quantization unit 208)may be configured to output QPs, e.g. directly or encoded via theentropy encoding unit 270, so that, e.g., the video decoder 30 mayreceive and apply the QPs for decoding.

Inverse Quantization:

The inverse quantization unit 210 is configured to apply the inversequantization of the quantization unit 208 on the quantized coefficientsto obtain dequantized coefficients 211, e.g. by applying the inverse ofthe quantization scheme applied by the quantization unit 208 based on orusing the same quantization step size as the quantization unit 208. Thedequantized coefficients 211 may also be referred to as dequantizedresidual coefficients 211 and correspond—although typically notidentical to the transform coefficients due to the loss byquantization—to the transform coefficients 207.

Inverse Transform:

The inverse transform processing unit 212 is configured to apply theinverse transform of the transform applied by the transform processingunit 206, e.g. an inverse DCT or inverse DST or other inversetransforms, to obtain a reconstructed residual block 213 (orcorresponding dequantized coefficients 213) in the sample domain. Thereconstructed residual block 213 may also be referred to as transformblock 213.

Reconstruction:

The reconstruction unit 214 (e.g. adder or summer 214) is configured toadd the transform block 213 (i.e. reconstructed residual block 213) tothe prediction block 265 to obtain a reconstructed block 215 in thesample domain, e.g. by adding—sample by sample—the sample values of thereconstructed residual block 213 and the sample values of the predictionblock 265.

Filtering:

The loop filter unit 220 (or short “loop filter” 220), is configured tofilter the reconstructed block 215 to obtain a filtered block 221, or ingeneral, to filter reconstructed samples to obtain filtered samples. Theloop filter unit is, e.g. configured to smooth pixel transitions, orotherwise improve the video quality. The loop filter unit 220 maycomprise one or more loop filters such as a de-blocking filter, asample-adaptive offset (SAO) filter or one or more other filters, e.g. abilateral filter, an adaptive loop filter (ALF), a sharpening, asmoothing filter or a collaborative filter, or any combination thereof.Although the loop filter unit 220 is shown in FIG. 2 as being an in loopfilter, in other configurations, the loop filter unit 220 may beimplemented as a post loop filter. The filtered block 221 may also bereferred to as filtered reconstructed block 221.

Embodiments of the video encoder 20 (respectively loop filter unit 220)may be configured to output loop filter parameters (such as sampleadaptive offset information), e.g. directly or encoded via the entropyencoding unit 270, so that, e.g., a decoder 30 may receive and apply thesame loop filter parameters or respective loop filters for decoding.

DPB:

The DPB 230 may be a memory that stores reference pictures, or ingeneral reference picture data, for encoding video data by video encoder20. The DPB 230 may be formed by any of a variety of memory devices,such as dynamic random-access memory (RAM) (DRAM), including synchronousDRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), orother types of memory devices. The DPB 230 may be configured to storeone or more filtered blocks 221. The DPB 230 may be further configuredto store other previously filtered blocks, e.g. previously reconstructedand filtered blocks 221, of the same current picture or of differentpictures, e.g. previously reconstructed pictures, and may providecomplete previously reconstructed, i.e. decoded, pictures (andcorresponding reference blocks and samples) and/or a partiallyreconstructed current picture (and corresponding reference blocks andsamples), for example for inter prediction. The DPB 230 may be alsoconfigured to store one or more unfiltered reconstructed blocks 215, orin general unfiltered reconstructed samples, e.g. if the reconstructedblock 215 is not filtered by loop filter unit 220, or any other furtherprocessed version of the reconstructed blocks or samples.

Mode Selection (Partitioning & Prediction):

The mode selection unit 260 comprises partitioning unit 262,inter-prediction unit 244 and intra-prediction unit 254, and isconfigured to receive or obtain original picture data, e.g. an originalblock 203 (current block 203 of the current picture 17), andreconstructed picture data, e.g. filtered and/or unfilteredreconstructed samples or blocks of the same (current) picture and/orfrom one or a plurality of previously decoded pictures, e.g. from DPB230 or other buffers (e.g. line buffer, not shown). The reconstructedpicture data is used as reference picture data for prediction, e.g.inter-prediction or intra-prediction, to obtain a prediction block 265or predictor 265.

Mode selection unit 260 may be configured to determine or select apartitioning for a current block prediction mode (including nopartitioning) and a prediction mode (e.g. an intra or inter predictionmode) and generate a corresponding prediction block 265, which is usedfor the calculation of the residual block 205 and for the reconstructionof the reconstructed block 215.

Embodiments of the mode selection unit 260 may be configured to selectthe partitioning and the prediction mode (e.g. from those supported byor available for mode selection unit 260), which provide the best matchor in other words the minimum residual (minimum residual means bettercompression for transmission or storage), or a minimum signalingoverhead (minimum signaling overhead means better compression fortransmission or storage), or which considers or balances both. The modeselection unit 260 may be configured to determine the partitioning andprediction mode based on rate distortion optimization (RDO), i.e. selectthe prediction mode which provides a minimum rate distortion. Terms like“best”, “minimum”, “optimum” etc. in this context do not necessarilyrefer to an overall “best”, “minimum”, “optimum”, etc. but may alsorefer to the fulfillment of a termination or selection criterion like avalue exceeding or falling below a threshold or other constraintsleading potentially to a “sub-optimum selection” but reducing complexityand processing time.

In other words, the partitioning unit 262 may be configured to partitionthe block 203 into smaller block partitions or sub-blocks (which againform blocks), e.g. iteratively using quad-tree (QT) partitioning,binary-tree (BT) partitioning, or triple-tree (TT) partitioning or anycombination thereof, and to perform, e.g., the prediction for each ofthe block partitions or sub-blocks, wherein the mode selection comprisesthe selection of the tree-structure of the partitioned block 203 and theprediction modes are applied to each of the block partitions orsub-blocks.

In the following the partitioning (e.g. by partitioning unit 260) andprediction processing (by inter-prediction unit 244 and intra-predictionunit 254) performed by an example video encoder 20 will be explained inmore detail.

Partitioning:

The partitioning unit 262 may partition (or split) a current block 203into smaller partitions, e.g. smaller blocks of square or rectangularsize. These smaller blocks (or sub-blocks) may be further partitionedinto even smaller partitions. This is also referred to tree-partitioningor hierarchical tree-partitioning, wherein a root block, e.g. at roottree-level 0 (hierarchy-level 0, depth 0), may be recursivelypartitioned, e.g. partitioned into two or more blocks of a next lowertree-level, e.g. nodes at tree-level 1 (hierarchy-level 1, depth 1),wherein these blocks may be again partitioned into two or more blocks ofa next lower level, e.g. tree-level 2 (hierarchy-level 2, depth 2), etc.until the partitioning is terminated, e.g. because a terminationcriterion is fulfilled, e.g. a maximum tree depth or minimum block sizeis reached. Blocks which are not further partitioned are also referredto as leaf-blocks or leaf nodes of the tree. A tree using partitioninginto two partitions is referred to as BT, a tree using partitioning intothree partitions is referred to as ternary-tree, and a tree usingpartitioning into four partitions is referred to as QT.

As mentioned before, the term “block” as used herein may be a portion,in particular a square or rectangular portion, of a picture. Withreference, for example, to HEVC and VVC, the block may be or correspondto a CTU, a CU, prediction unit (PU), and transform unit (TU) and/or tothe corresponding blocks, e.g. a CTB, a CB, a transform block (TB) orprediction block (PB).

For example, a CTU may be or comprise a CTB of luma samples, twocorresponding CTBs of chroma samples of a picture that has three samplearrays, or a CTB of samples of a monochrome picture or a picture that iscoded using three separate colour planes and syntax structures used tocode the samples. Correspondingly, a CTB may be an N×N block of samplesfor some value of N such that the division of a component into CTBs is apartitioning. A CU may be or comprise a coding block of luma samples,two corresponding coding blocks of chroma samples of a picture that hasthree sample arrays, or a coding block of samples of a monochromepicture or a picture that is coded using three separate colour planesand syntax structures used to code the samples. Correspondingly a CB maybe an M×N block of samples for some values of M and N such that thedivision of a CTB into coding blocks is a partitioning.

In embodiments, e.g., according to HEVC, a CTU may be split into CUs byusing a quad-tree structure denoted as coding tree. The decision whetherto code a picture area using inter-picture (temporal) or intra-picture(spatial) prediction is made at the CU level. Each CU can be furthersplit into one, two or four PUs according to the PU splitting type.Inside one PU, the same prediction process is applied and the relevantinformation is transmitted to the decoder on a PU basis. After obtainingthe residual block by applying the prediction process based on the PUsplitting type, a CU can be partitioned into transform units (TUs)according to another quadtree structure similar to the coding tree forthe CU.

In embodiments, e.g., according to the latest video coding standardcurrently in development, which is referred to as VVC, a combined QT andBT (QTBT) partitioning is for example used to partition a coding block.In the QTBT block structure, a CU can have either a square orrectangular shape. For example, a CTU is first partitioned by a quadtreestructure. The quadtree leaf nodes are further partitioned by a binarytree or ternary (or triple) tree structure. The partitioning tree leafnodes are called CUs, and that segmentation is used for prediction andtransform processing without any further partitioning. This means thatthe CU, PU and TU have the same block size in the QTBT coding blockstructure. In parallel, multiple partition, for example, TT partitionmay be used together with the QTBT block structure.

In one example, the mode selection unit 260 of video encoder 20 may beconfigured to perform any combination of the partitioning techniquesdescribed herein.

As described above, the video encoder 20 is configured to determine orselect the best or an optimum prediction mode from a set of (e.g.pre-determined) prediction modes. The set of prediction modes maycomprise, e.g., intra-prediction modes and/or inter-prediction modes.

Intra-Prediction:

The set of intra-prediction modes may comprise 35 differentintra-prediction modes, e.g. non-directional modes like DC (or mean)mode and planar mode, or directional modes, e.g. as defined in HEVC, ormay comprise 67 different intra-prediction modes, e.g. non-directionalmodes like DC (or mean) mode and planar mode, or directional modes, e.g.as defined for VVC.

The intra-prediction unit 254 is configured to use reconstructed samplesof neighboring blocks of the same current picture to generate anintra-prediction block 265 according to an intra-prediction mode of theset of intra-prediction modes.

The intra prediction unit 254 (or in general the mode selection unit260) is further configured to output intra-prediction parameters (or ingeneral information indicative of the selected intra prediction mode forthe block) to the entropy encoding unit 270 in form of syntax elements266 for inclusion into the encoded picture data 21, so that, e.g., thevideo decoder 30 may receive and use the prediction parameters fordecoding.

Inter-Prediction:

The set of (or possible) inter-prediction modes depends on the availablereference pictures (i.e. previous at least partially decoded pictures,e.g. stored in DBP 230) and other inter-prediction parameters, e.g.whether the whole reference picture or only a part, e.g. a search windowarea around the area of the current block, of the reference picture isused for searching for a best matching reference block, and/or e.g.whether pixel interpolation is applied, e.g. half/semi-pel and/orquarter-pel interpolation, or not.

Additional to the above prediction modes, skip mode and/or direct modemay be applied.

The inter prediction unit 244 may include a motion estimation (ME) unitand a motion compensation (MC) unit (both not shown in FIG. 2 ). Themotion estimation unit may be configured to receive or obtain thepicture block 203 (current picture block 203 of the current picture 17)and a decoded picture 231, or at least one or a plurality of previouslyreconstructed blocks, e.g. reconstructed blocks of one or a plurality ofother/different previously decoded pictures 231, for motion estimation.E.g. a video sequence may comprise the current picture and thepreviously decoded pictures 231, or in other words, the current pictureand the previously decoded pictures 231 may be part of or form asequence of pictures forming a video sequence.

The encoder 20 may, e.g., be configured to select a reference block froma plurality of reference blocks of the same or different pictures of theplurality of other pictures and provide a reference picture (orreference picture index) and/or an offset (spatial offset) between theposition (x, y coordinates) of the reference block and the position ofthe current block as inter prediction parameters to the motionestimation unit. This offset is also called MV.

The motion compensation unit is configured to obtain, e.g. receive, aninter prediction parameter and to perform inter prediction based on orusing the inter prediction parameter to obtain an inter prediction block265. Motion compensation, performed by the motion compensation unit, mayinvolve fetching or generating the prediction block based on themotion/block vector determined by motion estimation, possibly performinginterpolations to sub-pixel precision. Interpolation filtering maygenerate additional pixel samples from known pixel samples, thuspotentially increasing the number of candidate prediction blocks thatmay be used to code a picture block. Upon receiving the MV for the PU ofthe current picture block, the motion compensation unit may locate theprediction block to which the MV points in one of the reference picturelists.

The motion compensation unit may also generate syntax elementsassociated with the blocks and video slices for use by video decoder 30in decoding the picture blocks of the video slice. In addition or as analternative to slices and respective syntax elements, tile groups and/ortiles and respective syntax elements may be generated or used.

Entropy Coding:

The entropy encoding unit 270 is configured to apply, for example, anentropy encoding algorithm or scheme (e.g. a variable length coding(VLC) scheme, an context adaptive VLC scheme (CAVLC), an arithmeticcoding scheme, a binarization, a context adaptive binary arithmeticcoding (CABAC), syntax-based context-adaptive binary arithmetic coding(SBAC), probability interval partitioning entropy (PIPE) coding oranother entropy encoding methodology or technique) or bypass (nocompression) on the quantized coefficients 209, inter predictionparameters, intra prediction parameters, loop filter parameters and/orother syntax elements to obtain encoded picture data 21 which can beoutput via the output 272, e.g. in the form of an encoded bitstream 21,so that, e.g., the video decoder 30 may receive and use the parametersfor decoding. The encoded bitstream 21 may be transmitted to videodecoder 30, or stored in a memory for later transmission or retrieval byvideo decoder 30.

Other structural variations of the video encoder 20 can be used toencode the video stream. For example, a non-transform based encoder 20can quantize the residual signal directly without the transformprocessing unit 206 for certain blocks or frames. In anotherimplementation, an encoder 20 can have the quantization unit 208 and theinverse quantization unit 210 combined into a single unit.

Decoder and Decoding Method:

FIG. 3 shows an example of a video decoder 30 that is configured toimplement the techniques of this present application. The video decoder30 is configured to receive encoded picture data 21 (e.g. encodedbitstream 21), e.g. encoded by encoder 20, to obtain a decoded picture331. The encoded picture data or bitstream comprises information fordecoding the encoded picture data, e.g. data that represents pictureblocks of an encoded video slice (and/or tile groups or tiles) andassociated syntax elements.

In the example of FIG. 3 , the decoder 30 comprises an entropy decodingunit 304, an inverse quantization unit 310, an inverse transformprocessing unit 312, a reconstruction unit 314 (e.g. a summer 314), aloop filter 320, a DBP 330, a mode application unit 360, an interprediction unit 344 and an intra prediction unit 354. Inter predictionunit 344 may be or include a motion compensation unit. Video decoder 30may, in some examples, perform a decoding pass generally reciprocal tothe encoding pass described with respect to video encoder 20 from FIG. 2.

As explained with regard to the encoder 20, the inverse quantizationunit 210, the inverse transform processing unit 212, the reconstructionunit 214 the loop filter 220, the DPB 230, the inter prediction unit 344and the intra prediction unit 354 are also referred to as forming the“built-in decoder” of video encoder 20. Accordingly, the inversequantization unit 310 may be identical in function to the inversequantization unit 110, the inverse transform processing unit 312 may beidentical in function to the inverse transform processing unit 212, thereconstruction unit 314 may be identical in function to reconstructionunit 214, the loop filter 320 may be identical in function to the loopfilter 220, and the DPB 330 may be identical in function to the DPB 230.Therefore, the explanations provided for the respective units andfunctions of the video encoder 20 apply correspondingly to therespective units and functions of the video decoder 30.

Entropy Decoding:

The entropy decoding unit 304 is configured to parse the bitstream 21(or in general encoded picture data 21) and perform, for example,entropy decoding to the encoded picture data 21 to obtain, e.g.,quantized coefficients 309 and/or decoded coding parameters (not shownin FIG. 3 ), e.g. any or all of inter prediction parameters (e.g.reference picture index and MV), intra prediction parameter (e.g. intraprediction mode or index), transform parameters, QPs, loop filterparameters, and/or other syntax elements. Entropy decoding unit 304 maybe configured to apply the decoding algorithms or schemes correspondingto the encoding schemes as described with regard to the entropy encodingunit 270 of the encoder 20. Entropy decoding unit 304 may be furtherconfigured to provide inter prediction parameters, intra predictionparameter and/or other syntax elements to the mode application unit 360and other parameters to other units of the decoder 30. Video decoder 30may receive the syntax elements at the video slice level and/or thevideo block level. In addition or as an alternative to slices andrespective syntax elements, tile groups and/or tiles and respectivesyntax elements may be received and/or used.

Inverse Quantization:

The inverse quantization unit 310 may be configured to receive QPs (orin general information related to the inverse quantization) andquantized coefficients from the encoded picture data 21 (e.g. by parsingand/or decoding, e.g. by entropy decoding unit 304) and to apply basedon the QPs an inverse quantization on the decoded quantized coefficients309 to obtain dequantized coefficients 311, which may also be referredto as transform coefficients 311. The inverse quantization process mayinclude use of a QP determined by video encoder 20 for each video blockin the video slice (or tile or tile group) to determine a degree ofquantization and, likewise, a degree of inverse quantization that shouldbe applied.

Inverse Transform:

Inverse transform processing unit 312 may be configured to receivedequantized coefficients 311, also referred to as transform coefficients311, and to apply a transform to the dequantized coefficients 311 inorder to obtain reconstructed residual blocks 213 in the sample domain.The reconstructed residual blocks 213 may also be referred to astransform blocks 313. The transform may be an inverse transform, e.g.,an inverse DCT, an inverse DST, an inverse integer transform, or aconceptually similar inverse transform process. The inverse transformprocessing unit 312 may be further configured to receive transformparameters or corresponding information from the encoded picture data 21(e.g. by parsing and/or decoding, e.g. by entropy decoding unit 304) todetermine the transform to be applied to the dequantized coefficients311.

Reconstruction:

The reconstruction unit 314 (e.g. adder or summer 314) may be configuredto add the reconstructed residual block 313, to the prediction block 365to obtain a reconstructed block 315 in the sample domain, e.g. by addingthe sample values of the reconstructed residual block 313 and the samplevalues of the prediction block 365.

Filtering:

The loop filter unit 320 (either in the coding loop or after the codingloop) is configured to filter the reconstructed block 315 to obtain afiltered block 321, e.g. to smooth pixel transitions, or otherwiseimprove the video quality. The loop filter unit 320 may comprise one ormore loop filters such as a de-blocking filter, a sample-adaptive offset(SAO) filter or one or more other filters, e.g. a bilateral filter, anadaptive loop filter (ALF), a sharpening, a smoothing filters or acollaborative filters, or any combination thereof. Although the loopfilter unit 320 is shown in FIG. 3 as being an in loop filter, in otherconfigurations, the loop filter unit 320 may be implemented as a postloop filter.

DPB:

The decoded video blocks 321 of a picture are then stored in DPB 330,which stores the decoded pictures 331 as reference pictures forsubsequent motion compensation for other pictures and/or for outputrespectively display.

The decoder 30 is configured to output the decoded picture 311, e.g. viaoutput 312, for presentation or viewing to a user.

Prediction:

The inter prediction unit 344 may be identical to the inter predictionunit 244 (in particular to the motion compensation unit) and the intraprediction unit 354 may be identical to the inter prediction unit 254 infunction, and performs split or partitioning decisions and predictionbased on the partitioning and/or prediction parameters or respectiveinformation received from the encoded picture data 21 (e.g. by parsingand/or decoding, e.g. by entropy decoding unit 304). Mode applicationunit 360 may be configured to perform the prediction (intra or interprediction) per block based on reconstructed pictures, blocks orrespective samples (filtered or unfiltered) to obtain the predictionblock 365.

When the video slice is coded as an intra coded (I) slice, intraprediction unit 354 of mode application unit 360 is configured togenerate prediction block 365 for a picture block of the current videoslice based on a signaled intra prediction mode and data from previouslydecoded blocks of the current picture. When the video picture is codedas an inter coded (i.e., B, or P) slice, inter prediction unit 344 (e.g.motion compensation unit) of mode application unit 360 is configured toproduce prediction blocks 365 for a video block of the current videoslice based on the MVs and other syntax elements received from entropydecoding unit 304. For inter prediction, the prediction blocks may beproduced from one of the reference pictures within one of the referencepicture lists. Video decoder 30 may construct the reference frame lists,List 0 and List 1, using default construction techniques based onreference pictures stored in DPB 330. The same or similar may be appliedfor or by embodiments using tile groups (e.g. video tile groups) and/ortiles (e.g. video tiles) in addition or alternatively to slices (e.g.video slices), e.g. a video may be coded using I, P or B tile groupsand/or tiles.

Mode application unit 360 is configured to determine the predictioninformation for a video block of the current video slice by parsing theMVs or related information and other syntax elements, and uses theprediction information to produce the prediction blocks for the currentvideo block being decoded. For example, the mode application unit 360uses some of the received syntax elements to determine a prediction mode(e.g., intra or inter prediction) used to code the video blocks of thevideo slice, an inter prediction slice type (e.g., B slice, P slice, orGPB slice), construction information for one or more of the referencepicture lists for the slice, MVs for each inter encoded video block ofthe slice, inter prediction status for each inter coded video block ofthe slice, and other information to decode the video blocks in thecurrent video slice. The same or similar may be applied for or byembodiments using tile groups (e.g. video tile groups) and/or tiles(e.g. video tiles) in addition or alternatively to slices (e.g. videoslices), e.g. a video may be coded using I, P or B tile groups and/ortiles.

Embodiments of the video decoder 30 as shown in FIG. 3 may be configuredto partition and/or decode the picture by using slices (also referred toas video slices), wherein a picture may be partitioned into or decodedusing one or more slices (typically non-overlapping), and each slice maycomprise one or more blocks (e.g. CTUs).

Embodiments of the video decoder 30 as shown in FIG. 3 may be configuredto partition and/or decode the picture by using tile groups (or videotile groups) and/or tiles (or video tiles), wherein a picture may bepartitioned into or decoded using one or more tile groups (typicallynon-overlapping), and each tile group may comprise, e.g. one or moreblocks (e.g. CTUs) or one or more tiles, wherein each tile, e.g. may beof rectangular shape and may comprise one or more blocks (e.g. CTUs),e.g. complete or fractional blocks.

Other variations of the video decoder 30 can be used to decode theencoded picture data 21. For example, the decoder 30 can produce theoutput video stream without the loop filtering unit 320. For example, anon-transform based decoder 30 can inverse-quantize the residual signaldirectly without the inverse-transform processing unit 312 for certainblocks or frames. In another implementation, the video decoder 30 canhave the inverse-quantization unit 310 and the inverse-transformprocessing unit 312 combined into a single unit.

It should be understood that, in the encoder 20 and the decoder 30, aprocessing result of a current step may be further processed and thenoutput to the next step. For example, after interpolation filtering, MVderivation or loop filtering, a further operation, such as Clip orshift, may be performed on the processing result of the interpolationfiltering, MV derivation or loop filtering.

It should be noted that further operations may be applied to the derivedMVs of current block (including but not limit to control point MVs ofaffine mode, sub-block MVs in affine, planar, ATMVP modes, temporal MVs,and so on). For example, the value of MV is constrained to a predefinedrange according to its representing bit. If the representing bit of MVis bitDepth, then the range is −2{circumflex over( )}(bitDepth-1)˜2{circumflex over ( )}(bitDepth-1)−1, where“{circumflex over ( )}” means exponentiation. For example, if bitDepthis set equal to 16, the range is −32768˜32767, if bitDepth is set equalto 18, the range is −131072˜131071. For example, the value of thederived MV (e.g. the MVs of four 4×4 sub-blocks within one 8×8 block) isconstrained such that the max difference between integer parts of thefour 4×4 sub-block MVs is no more than N pixels, such as no more than 1pixel. Here provides two methods for constraining the MV according tothe bitDepth.

Method 1: remove the overflow most significant bit (MSB) by flowingoperations:ux=(mvx+2^(bitDepth))%2^(bitDepth)  (1)mvx=(ux>=2^(bitDepth-1))?(ux−2^(bitDepth)):ux,  (2)uy=(mvy+2^(bitDepth))%2^(bitDepth), and  (3)mvy=(uy>=2^(bitDepth-1))?(uy−2^(bitDepth)):uy,  (4)where mvx is a horizontal component of a MV of an image block or asub-block, mvy is a vertical component of a MV of an image block or asub-block, and ux and uy indicates an intermediate value.

For example, if the value of mvx is −32769, after applying formula (1)and (2), the resulting value is 32767. In computer system, decimalnumbers are stored as two's complement. The two's complement of −32769is 1,0111,1111,1111,1111 (17 bits), then the MSB is discarded, so theresulting two's complement is 0111,1111,1111,1111 (decimal number is32767), which is same as the output by applying formula (1) and (2):ux=(mvpx+mvdx+2^(bitDepth))%2^(bitDepth),  (5)mvx=(ux>=2^(bitDepth-1))?(ux−2^(bitDepth)):ux,  (6)uy=(mvpy+mvdy2^(bitDepth))%2^(bitDepth), and  (7)mvy=(uy>=2^(bitDepth-1))?(uy−2^(bitDepth)):uy.  (8)

The operations may be applied during the sum of mvp and mvd, as shown informula (5) to (8).

Method 2: Remove the overflow MSB by clipping the value:vx=Clip3(−2^(bitDepth-1),2^(bitDepth-1)−1,vx), andvy=Clip3(−2^(bitDepth-1),2^(bitDepth-1)−1,vy),where vx is a horizontal component of a MV of an image block or asub-block, vy is a vertical component of a MV of an image block or asub-block, x, y and z respectively correspond to three input value ofthe MV clipping process, and the definition of function Clip3 is asfollow:

${{Clip}\; 3\left( {x,\ y,\ z} \right)} = \left\{ \begin{matrix}{x;} & {z < x} \\{y;} & {z > y} \\{z;} & {otherwise}\end{matrix} \right.$

FIG. 5 is a schematic diagram of a video coding device 400 according toan embodiment of the disclosure. The video coding device 400 is suitablefor implementing the disclosed embodiments as described herein. In anembodiment, the video coding device 400 may be a decoder such as videodecoder 30 of FIG. 1A or an encoder such as video encoder 20 of FIG. 1A.

The video coding device 400 comprises ingress ports 410 (or input ports410) and receiver units (Rx) 420 for receiving data, a processor, logicunit, or central processing unit (CPU) 430 to process the data,transmitter units (Tx) 440 and egress ports 450 (or output ports 450)for transmitting the data, and a memory 460 for storing the data. Thevideo coding device 400 may also comprise optical-to-electrical (OE)components and electrical-to-optical (EO) components coupled to theingress ports 410, the receiver units 420, the transmitter units 440,and the egress ports 450 for egress or ingress of optical or electricalsignals.

The processor 430 is implemented by hardware and software. The processor430 may be implemented as one or more CPU chips, cores (e.g., as amulti-core processor), FPGAs, ASICs, and DSPs. The processor 430 is incommunication with the ingress ports 410, receiver units 420,transmitter units 440, egress ports 450, and memory 460. The processor430 comprises a coding module 470. The coding module 470 implements thedisclosed embodiments described above. For instance, the coding module470 implements, processes, prepares, or provides the various codingoperations. The inclusion of the coding module 470 therefore provides asubstantial improvement to the functionality of the video coding device400 and effects a transformation of the video coding device 400 to adifferent state. Alternatively, the coding module 470 is implemented asinstructions stored in the memory 460 and executed by the processor 430.

The memory 460 may comprise one or more disks, tape drives, andsolid-state drives and may be used as an over-flow data storage device,to store programs when such programs are selected for execution, and tostore instructions and data that are read during program execution. Thememory 460 may be, for example, volatile and/or non-volatile and may bea read-only memory (ROM), RAM, ternary content-addressable memory(TCAM), and/or static RAM (SRAM).

FIG. 6 is a simplified block diagram of an apparatus 500 that may beused as either or both of the source device 12 and the destinationdevice 14 from FIG. 1A according to an exemplary embodiment.

A processor 502 in the apparatus 500 can be a central processing unit.Alternatively, the processor 502 can be any other type of device, ormultiple devices, capable of manipulating or processing informationnow-existing or hereafter developed. Although the disclosedimplementations can be practiced with a single processor as shown, e.g.,the processor 502, advantages in speed and efficiency can be achievedusing more than one processor.

A memory 504 in the apparatus 500 can be a ROM device or a RAM device inan implementation. Any other suitable type of storage device can be usedas the memory 504. The memory 504 can include code and data 506 that isaccessed by the processor 502 using a bus 512. The memory 504 canfurther include an operating system 508 and application programs 510,the application programs 510 including at least one program that permitsthe processor 502 to perform the methods described here. For example,the application programs 510 can include applications 1 through N, whichfurther include a video coding application that performs the methodsdescribed here.

The apparatus 500 can also include one or more output devices, such as adisplay 518. The display 518 may be, in one example, a touch sensitivedisplay that combines a display with a touch sensitive element that isoperable to sense touch inputs. The display 518 can be coupled to theprocessor 502 via the bus 512.

Although depicted here as a single bus, the bus 512 of the apparatus 500can be composed of multiple buses. Further, the secondary storage 514can be directly coupled to the other components of the apparatus 500 orcan be accessed via a network and can comprise a single integrated unitsuch as a memory card or multiple units such as multiple memory cards.The apparatus 500 can thus be implemented in a wide variety ofconfigurations.

Embodiments of this disclosure are based on the LIC which is describedin CE10.5.2 (NET-M0087). CE10.5.2 can achieve the basement pipelinestructure with LIC, but still could use one extra stage cycle issue insome cases. One of the cases is a very simple modes of Intra prediction,like DC mode or integer slope directional modes. In parallel encoding oftiles it could be quite often a case in the top left corner of eachtile. In these cases (which are usually exploited by commercial fastencoders) motion compensation stage or pipeline could have higherlatency that Intra prediction. In another scenario like Multi HypothesesIntra prediction (Combined Inter-Intra prediction—CIIP) Intra pipelineat the beginning of the picture/tile or another coding unit could befaster than Inter prediction of the unit with fractional MC. For suchcases and for similar cases other approach designs of LIC should waitfor the finalization of MC stage. Moreover, LIC parameter estimationsuse samples outside of the current prediction unit which lead to memorybandwidth increase. Embodiments of this disclosure try to reduce thelatency of LIC for described and similar cases.

As shown in FIG. 7A, the design of the pipeline proposed in embodimentsof this disclosure operates with non-fractional motion compensated data(just samples taken from a reference frame without interpolation). Itallows to start processing of LIC unit in parallel with MC. Due toabsence of filtering process for these lines it is allow to keep memorybandwidth in the same level as without LIC.

Using unfiltered reference samples for LIC parameter estimation.

For Inter prediction of current block containing array of samplesCU[i,j] of size W×H with available reference samples Top [i] with i=0 .. . W and Left[j] with j=0 . . . H and available MV(mvx, mvy) stored inprecision mvp the LIC processing includes the following steps: LICparameter (linear approximation A*x+B) estimated between reference linesTop[i], Left[j] and collocated samples taken from the reference frameusing the integer part of MV (mvx,mvy) (Imvx=(mvx>>mvp)<<mvp,Imvy=(mvy>>mvp)<<mvp). The mvp is a constant to represent the MVprecision. For example, the mvp is 2. The LIC parameters are applied foreach prediction direction separately.

In another possible implementation the LIC processing includes followingsteps: LIC parameter (linear approximation A*x+B) estimated betweenreference lines Top[i], Left[j] and collocated samples taken from thereference frame using the integer part of one of the components of MV(mvx,mvy) (Imvx=(mvx>>mvp)<<mvp, mvy). The mvp is a constant torepresent the MV precision. For example, the mvp is 2. The LICparameters are applied for each prediction direction separately.

FIG. 7B is an exemplary figure with LIC based on integer pel motioncompensation. As the example shown on FIG. 7B, the arrow 701 correspondsto actual MV of the current block (mvx,mvy) which is used for motioncompensation stage. In embodiments of this disclosure, the integer partof MV is proposed to use MVinteger (Imvx,Imvy) as depicted by the arrow702 on FIG. 7B. Top reference samples 703-706, and/or left referencesamples 710-713, are used for LIC parameters estimation.

FIG. 8 is a flowchart 800 illustrating exemplary inter prediction of acurrent block by applying LIC. At step 802, a video coding deviceobtains reference samples of the current block. The video coding devicemay be a decoder such as video decoder 30 of FIG. 1A-1B, FIG. 3 , or anencoder such as video encoder 20 of FIG. 1A-1B, FIG. 2 , or Video CodingDevice 400 of FIG. 4 , or the apparatus 500 of FIG. 5 .

The reference samples of the current block are obtained from referencelines Top[i], Left[j], wherein Top[i] represents available top referencesamples of the current block, i=0 . . . W and Left[j] representsavailable left reference samples of the current block, j=0 . . . H, Wrepresents the width of the current block, and H represents the heightof the current block.

At step 804, the video coding device obtains reference samples of areference block, where at least one of the reference samples of thereference block is obtained by using the integer part of a fractionalMV. Reference samples of the reference block are called the referencesamples of the reference block.

As an example, at least one of the reference samples of the referenceblock is obtained by following:(Imvx=(mvx>>mvp)<<mvp,Imvy=(mvy>>mvp)<<mvp),wherein (Imvx, Imvy) is MV of one of the reference samples, (mvx, mvy)is the fractional MV, and mvp is a constant.

As another example, at least one of the reference samples of thereference block is obtained by following:(Imvx=(mvx>>mvp)<<mvp,Imvy=mvy),wherein (Imvx, Imvy) is MV of one of the reference samples, (mvx, mvy)is the fractional MV, and mvp is a constant.

As other example, at least one of the reference samples of the referenceblock is obtained by following:(Imvx=mvx,Imvy=(mvy>>mvp)<<mvp),wherein (Imvx, Imvy) is MV of one of the reference samples, (mvx, mvy)is the fractional MV, and mvp is a constant.

At step 806, the video coding device estimates LIC parameters by usingreference samples of the current block and reference samples of thereference block.

The LIC parameters include A and B, and the LIC parameters are estimatedby linear approximation.

At step 808, the video coding device obtains inter prediction of thecurrent block according to the LIC parameters. The inter prediction ofthe current block satisfies: Y=A*x+B, where Y is the inter prediction ofthe current block, x is reference samples of the reference block, A andB are the LIC parameters.

As disclosed in exemplary method 800, at least one of the referencesamples of the reference block is obtained by using the integer part ofa fractional MV. This scheme allows reduce the latency by dropping onestage. Therefore, it is a simplification for inter prediction of thecurrent block when reference samples (i.e., reference samples) ofreference block include the fractional MV.

FIG. 9 is a block diagram showing an example structure of an apparatus900 for inter prediction of a current block by applying LIC. Theapparatus 900 is configured to carry out the above methods, and mayinclude an estimating unit 910 and an obtaining unit 920.

The obtaining unit 920 configured to obtain reference samples of areference block, wherein at least one of the reference samples of thereference block is obtained by using the integer part of a fractionalMV.

As an example, at least one of the reference samples of the referenceblock is obtained by following:(Imvx=(mvx>>mvp)<<mvp,Imvy=(mvy>>mvp)<<mvp),wherein (Imvx, Imvy) is MV of one of the reference samples of thereference block, (mvx, mvy) is the fractional MV, and mvp is a constant.

As another example, at least one of the reference samples of thereference block is obtained by following:(Imvx=(mvx>>mvp)<<mvp,Imvy=mvy),wherein (Imvx, Imvy) is MV of one of the reference samples of thereference block, (mvx, mvy) is the fractional MV, and mvp is a constant.

As other example, at least one of the reference samples of the referenceblock is obtained by following:(Imvx=mvx,Imvy=(mvy>>mvp)<<mvp),wherein (Imvx, Imvy) is MV of one of the reference samples of thereference block, (mvx, mvy) is the fractional MV, and mvp is a constant.

The estimating unit 910 configured to estimate LIC parameters by usingreference samples of a current block and the reference samples of thereference block. For example, the estimating unit 910 estimates the LICparameters by linear approximation.

The obtaining unit 920 configured to obtain inter prediction of thecurrent block according to the LIC parameters.

The obtaining unit 920, further configured to obtain the referencesamples of the current block from reference lines Top[i], Left[j],wherein Top[i] represents available top reference samples of the currentblock, i=0 . . . W, W represents the width of the current block, andwherein Left[j] represents available left reference samples of thecurrent block, j=0 . . . H, H represents the height of the currentblock.

The estimating unit 910 is configured to estimate LIC parameters inparallel with performing motion compensation (MC)

As disclosed in exemplary apparatus 900, at least one of the referencesamples of the reference block is obtained by using the integer part ofa fractional MV. This scheme allows reduce the latency by dropping onestage. Therefore, it is a simplification for inter prediction of thecurrent block when reference samples (i.e., reference samples) ofreference block include the fractional MV.

Following is an explanation of the applications of the encoding methodas well as the decoding method as shown in the above-mentionedembodiments, and a system using them.

FIG. 10 is a block diagram showing a content supply system 3100 forrealizing content distribution service. This content supply system 3100includes capture device 3102, terminal device 3106, and optionallyincludes display 3126. The capture device 3102 communicates with theterminal device 3106 over communication link 3104. The communicationlink may include the communication channel 13 described above. Thecommunication link 3104 includes but not limited to WI-FI, Ethernet,Cable, wireless (third generation (3G)/fourth generation (4G)/fifthgeneration (5G)), Universal Serial Bus (USB), or any kind of combinationthereof, or the like.

The capture device 3102 generates data, and may encode the data by theencoding method as shown in the above embodiments. Alternatively, thecapture device 3102 may distribute the data to a streaming server (notshown in the Figures), and the server encodes the data and transmits theencoded data to the terminal device 3106. The capture device 3102includes but not limited to camera, smart phone or IPAD, computer orlaptop, video conference system, personal digital assistant (PDA),vehicle mounted device, or a combination of any of them, or the like.For example, the capture device 3102 may include the source device 12 asdescribed above. When the data includes video, the video encoder 20included in the capture device 3102 may actually perform video encodingprocessing. When the data includes audio (i.e., voice), an audio encoderincluded in the capture device 3102 may actually perform audio encodingprocessing. For some practical scenarios, the capture device 3102distributes the encoded video and audio data by multiplexing themtogether. For other practical scenarios, for example in the videoconference system, the encoded audio data and the encoded video data arenot multiplexed. Capture device 3102 distributes the encoded audio dataand the encoded video data to the terminal device 3106 separately.

In the content supply system 3100, the terminal device 310 receives andreproduces the encoded data. The terminal device 3106 could be a devicewith data receiving and recovering capability, such as smart phone orPad 3108, computer or laptop 3110, network video recorder (NVR)/digitalvideo recorder (DVR) 3112, TV 3114, set top box (STB) 3116, videoconference system 3118, video surveillance system 3120, PDA 3122,vehicle mounted device 3124, or a combination of any of them, or thelike capable of decoding the above-mentioned encoded data. For example,the terminal device 3106 may include the destination device 14 asdescribed above. When the encoded data includes video, the video decoder30 included in the terminal device is prioritized to perform videodecoding. When the encoded data includes audio, an audio decoderincluded in the terminal device is prioritized to perform audio decodingprocessing.

For a terminal device with its display, for example, smart phone or Pad3108, computer or laptop 3110, NVR/DVR 3112, TV 3114, PDA 3122, orvehicle mounted device 3124, the terminal device can feed the decodeddata to its display. For a terminal device equipped with no display, forexample, STB 3116, video conference system 3118, or video surveillancesystem 3120, an external display 3126 is contacted therein to receiveand show the decoded data.

When each device in this system performs encoding or decoding, thepicture encoding device or the picture decoding device, as shown in theabove-mentioned embodiments, can be used.

FIG. 11 is a diagram showing a structure of an example of the terminaldevice 3106. After the terminal device 3106 receives stream from thecapture device 3102, the protocol proceeding unit 3202 analyzes thetransmission protocol of the stream. The protocol includes but notlimited to Real Time Streaming Protocol (RTSP), Hyper Text TransferProtocol (HTTP), HTTP Live streaming protocol (HLS), MPEG—DynamicAdaptive Streaming over HTTP (DASH), Real-time Transport protocol (RTP),Real Time Messaging Protocol (RTMP), or any kind of combination thereof,or the like.

After the protocol proceeding unit 3202 processes the stream, streamfile is generated. The file is outputted to a demultiplexing unit 3204.The demultiplexing unit 3204 can separate the multiplexed data into theencoded audio data and the encoded video data. As described above, forsome practical scenarios, for example in the video conference system,the encoded audio data and the encoded video data are not multiplexed.In this situation, the encoded data is transmitted to video decoder 3206and audio decoder 3208 without through the demultiplexing unit 3204.

Via the demultiplexing processing, video elementary stream (ES), audioES, and optionally subtitle are generated. The video decoder 3206, whichincludes the video decoder 30 as explained in the above mentionedembodiments, decodes the video ES by the decoding method as shown in theabove-mentioned embodiments to generate video frame, and feeds this datato the synchronous unit 3212. The audio decoder 3208, decodes the audioES to generate audio frame, and feeds this data to the synchronous unit3212. Alternatively, the video frame may store in a buffer (not shown inFIG. 11 ) before feeding it to the synchronous unit 3212. Similarly, theaudio frame may store in a buffer (not shown in FIG. 11 ) before feedingit to the synchronous unit 3212.

The synchronous unit 3212 synchronizes the video frame and the audioframe, and supplies the video/audio to a video/audio display 3214. Forexample, the synchronous unit 3212 synchronizes the presentation of thevideo and audio information. Information may code in the syntax usingtime stamps concerning the presentation of coded audio and visual dataand time stamps concerning the delivery of the data stream itself.

If subtitle is included in the stream, the subtitle decoder 3210 decodesthe subtitle, and synchronizes it with the video frame and the audioframe, and supplies the video/audio/subtitle to a video/audio/subtitledisplay 3216.

Mathematical Operators:

The mathematical operators used in this application are similar to thoseused in the C programming language. However, the results of integerdivision and arithmetic shift operations are defined more precisely, andadditional operations are defined, such as exponentiation andreal-valued division. Numbering and counting conventions generally beginfrom 0, e.g., “the first” is equivalent to the 0-th, “the second” isequivalent to the 1-th, etc.

Arithmetic Operators:

The following arithmetic operators are defined as follows:

-   -   + Addition    -   − Subtraction (as a two-argument operator) or negation (as a        unary prefix operator)    -   * Multiplication, including matrix multiplication    -   x^(y) Exponentiation. Specifies x to the power of y. In other        contexts, such notation is used for superscripting not intended        for interpretation as exponentiation.    -   / Integer division with truncation of the result toward zero.        For example, 7/4 and −7/−4 are truncated to 1 and −7/4 and 7/−4        are truncated to −1.    -   ÷ Used to denote division in mathematical equations where no        truncation or rounding is intended.

$\begin{matrix}\frac{x}{y} & \begin{matrix}{{{Used}\mspace{14mu}{to}\mspace{14mu}{denote}\mspace{14mu}{division}\mspace{14mu}{in}\mspace{14mu}{mathematical}\mspace{14mu}{equations}}\;} \\{{where}\mspace{14mu}{no}\mspace{14mu}{truncation}\mspace{14mu}{or}\mspace{14mu}{rounding}\mspace{14mu}{is}\mspace{14mu}{{intended}.}}\end{matrix} \\{\sum\limits_{i = x}^{y}{f(i)}} & \begin{matrix}{{The}\mspace{14mu}{summation}\mspace{14mu}{of}\mspace{14mu}{f(i)}\mspace{14mu}{with}\mspace{14mu} i\mspace{14mu}{taking}\mspace{14mu}{all}\mspace{14mu}{integer}\mspace{14mu}{values}} \\{{from}\mspace{14mu} x\mspace{14mu}{up}\mspace{14mu}{to}\mspace{14mu}{and}\mspace{14mu}{including}\mspace{14mu}{y.}}\end{matrix}\end{matrix}$

-   -   x % y Modulus. Remainder of x divided by y, defined only for        integers x and y with x>=0 and y>0.

Logical Operators:

The following logical operators are defined as follows:

-   -   x && y Boolean logical “and” of x and y    -   x∥y Boolean logical “or” of x and y    -   ! Boolean logical “not”    -   x ? y:z If x is TRUE or not equal to 0, evaluates to the value        of y; otherwise, evaluates to the value of z.

Relational Operators:

The following relational operators are defined as follows:

-   -   > Greater than    -   >= Greater than or equal to    -   < Less than    -   <= Less than or equal to    -   == Equal to    -   != Not equal to

When a relational operator is applied to a syntax element or variablethat has been assigned the value “na” (not applicable), the value “na”is treated as a distinct value for the syntax element or variable. Thevalue “na” is considered not to be equal to any other value.

Bit-Wise Operators:

The following bit-wise operators are defined as follows:

-   -   & Bit-wise “and”. When operating on integer arguments, operates        on a two's complement representation of the integer value. When        operating on a binary argument that contains fewer bits than        another argument, the shorter argument is extended by adding        more significant bits equal to 0.    -   | Bit-wise “or”. When operating on integer arguments, operates        on a two's complement representation of the integer value. When        operating on a binary argument that contains fewer bits than        another argument, the shorter argument is extended by adding        more significant bits equal to 0.    -   {circumflex over ( )} Bit-wise “exclusive or”. When operating on        integer arguments, operates on a two's complement representation        of the integer value. When operating on a binary argument that        contains fewer bits than another argument, the shorter argument        is extended by adding more significant bits equal to 0.    -   x>>y Arithmetic right shift of a two's complement integer        representation of x by y binary digits. This function is defined        only for non-negative integer values of y. Bits shifted into the        most significant bits (MSBs) as a result of the right shift have        a value equal to the MSB of x prior to the shift operation.    -   x<<y Arithmetic left shift of a two's complement integer        representation of x by y binary digits. This function is defined        only for non-negative integer values of y. Bits shifted into the        least significant bits (LSBs) as a result of the left shift have        a value equal to 0.

Assignment Operators:

The following arithmetic operators are defined as follows:

-   -   = Assignment operator    -   ++ Increment, i.e., x++ is equivalent to x=x+1, when used in an        array index, evaluates to the value of the variable prior to the        increment operation.    -   −− Decrement, i.e., x−− is equivalent to x=x−1, when used in an        array index, evaluates to the value of the variable prior to the        decrement operation.    -   += Increment by amount specified, i.e., x+=3 is equivalent to        x=x+3, and x+=(−3) is equivalent to x=x+(−3).    -   −= Decrement by amount specified, i.e., x−=3 is equivalent to        x=x−3, and x−=(−3) is equivalent to x=x−(−3).

Range Notation:

The following notation is used to specify a range of values:

-   -   x=y . . . z x takes on integer values starting from y to z,        inclusive, with x, y, and z being integer numbers and z being        greater than y.

Mathematical Functions

The following mathematical functions are defined:

${{Abs}(x)} = \left\{ \begin{matrix}{x;} & {x>=0} \\{{- x};} & {x < 0}\end{matrix} \right.$

-   -   A sin(x) the trigonometric inverse sine function, operating on        an argument x that is in the range of −1.0 to 1.0, inclusive,        with an output value in the range of −π÷2 to π÷2, inclusive, in        units of radians    -   A tan(x) the trigonometric inverse tangent function, operating        on an argument x, with an output value in the range of −π÷2 to        π÷2, inclusive, in units of radians

${A\tan 2\left( {y,x} \right)} = \left\{ \begin{matrix}{{A\;{\tan\ \left( \frac{y}{x} \right)}};} & {x > 0} \\{{{A\;{\tan\ \left( \frac{y}{x} \right)}} + \pi};} & {{{{{x < 0}\ \&}\&}\ y}>=0} \\{{{A\;{\tan\ \left( \frac{y}{x} \right)}} - \pi};} & {{{{{x < 0}\ \&}\&}\ y} < 0} \\{{+ \frac{\pi}{2}};} & {{x==0}\&\&{y>=0}} \\{{- \frac{\pi}{2}};} & {otherwise}\end{matrix} \right.$

-   -   Ceil(x) the smallest integer greater than or equal to x.    -   Clip1_(Y)(x)=Clip3(0, (1<<BitDepth_(Y))−1, x)    -   Clip1_(C)(x)=Clip3(0, (1<<BitDepth_(C))−1, x)

${{Clip}\; 3\left( {x,\ y,\ z} \right)} = \left\{ \begin{matrix}{x;} & {z < x} \\{y;} & {z > y} \\{z;} & {otherwise}\end{matrix} \right.$

-   -   Cos(x) the trigonometric cosine function operating on an        argument x in units of radians.    -   Floor(x) the largest integer less than or equal to x.

${{Get}\;{{CurrMsb}\left( {a,b,c,d} \right)}} = \left\{ \begin{matrix}{{c + d};} & {{b - a}>={d/2}} \\{{c - d};} & {{a - b} > {d/2}} \\{c;} & {otherwise}\end{matrix} \right.$

-   -   Ln(x) the natural logarithm of x (the base-e logarithm, where e        is the natural logarithm base constant 2.718281828 . . . ).    -   Log 2(x) the base-2 logarithm of x.    -   Log 10(x) the base-10 logarithm of x.

$\begin{matrix}{{{Min}\left( {x,y} \right)} =} & \left\{ \begin{matrix}{x;} & {x<=y} \\{y;} & {x > y}\end{matrix} \right. \\{{{Max}\left( {x,y} \right)} =} & \left\{ \begin{matrix}{x;} & {x>=y} \\{y;} & {x < y}\end{matrix} \right.\end{matrix}$

-   -   Round(x)=Sign(x)*Floor(Abs(x)+0.5)

${{Sign}(x)} = \left\{ \begin{matrix}{1;} & {x > 0} \\{0;} & {x==0} \\{{- 1};} & {x < 0}\end{matrix} \right.$

-   -   Sin(x) the trigonometric sine function operating on an argument        x in units of radians    -   Sqrt(x)=√{square root over (x)}    -   Swap(x, y)=(y, x)    -   Tan(x) the trigonometric tangent function operating on an        argument x in units of radians

Order of Operation Precedence:

When an order of precedence in an expression is not indicated explicitlyby use of parentheses, the following rules apply:

Operations of a higher precedence are evaluated before any operation ofa lower precedence.

Operations of the same precedence are evaluated sequentially from leftto right.

The table below specifies the precedence of operations from highest tolowest, a higher position in the table indicates a higher precedence.

For those operators that are also used in the C programming language,the order of precedence used in this Specification is the same as usedin the C programming language.

TABLE Operation precedence from highest (at top of table) to lowest (atbottom of table) operations (with operands x, y, and z) ″x++″, ″x−−″″!x″, ″−x″ (as a unary prefix operator) x^(y)${{\,^{''}x}*y^{''}},{{\,^{''}x}\text{/}y^{''}},{{\,^{''}x} \div y^{''}},{{\,^{''}\frac{x}{y}}\,^{''}},{{\,^{''}x}\mspace{14mu}\%\mspace{14mu} y^{''}}$″x + y″, ″x − y″ (as a two-argument operator),$\,^{''}{\sum\limits_{i = x}^{y}\;{{f(i)}\,^{''}}}$ ″x << y″, ″x >> y″″x < y″, ″x <= y″, ″x > y″, ″x >= y″ ″x = = y″, ″x != y″ ″x & y″ ″x|y″″x && y″ ″x∥y″ ″x ? y : z″ ″x . . . y″ ″x = y″, ″x += y″, ″x −= y″

Text Description of Logical Operations:

In the text, a statement of logical operations as would be describedmathematically in the following form:

-   -   if(condition 0)        -   statement 0    -   else if(condition 1)        -   statement 1    -   . . .    -   else /* informative remark on remaining condition */statement        -   statement n            may be described in the following manner:    -   . . . as follows / . . . the following applies:    -   If condition 0, statement 0

Otherwise, if condition 1, statement 1

-   -   . . .

Otherwise (informative remark on remaining condition), statement n

Each “If . . . Otherwise, if . . . Otherwise, . . . ” statement in thetext is introduced with “ . . . as follows” or “ . . . the followingapplies” immediately followed by “If . . . ”. The last condition of the“If . . . Otherwise, if . . . Otherwise, . . . ” is always an“Otherwise, . . . ”. Interleaved “If . . . Otherwise, if . . .Otherwise, . . . ” statements can be identified by matching “ . . . asfollows” or “ . . . the following applies” with the ending “Otherwise, .. . ”.

In the text, a statement of logical operations as would be describedmathematically in the following form:

-   -   if(condition 0a && condition 0b)        -   statement 0    -   else if(condition 1a∥condition 1b)        -   statement 1    -   . . .    -   else        -   statement n            may be described in the following manner:    -   . . . as follows / . . . the following applies:    -   If all of the following conditions are true, statement 0:        -   condition 0a        -   condition 0b

Otherwise, if one or more of the following conditions are true,statement 1:

-   -   condition 1a    -   condition 1b    -   . . .

Otherwise, statement n

In the text, a statement of logical operations as would be describedmathematically in the following form:

-   -   if(condition 0)        -   statement 0    -   if(condition 1)        -   statement 1            may be described in the following manner:    -   When condition 0, statement 0    -   When condition 1, statement 1

Although embodiments of the disclosure have been primarily describedbased on video coding, it should be noted that embodiments of the codingsystem 10, encoder 20 and decoder 30 (and correspondingly the system 10)and the other embodiments described herein may also be configured forstill picture processing or coding, i.e. the processing or coding of anindividual picture independent of any preceding or consecutive pictureas in video coding. In general only inter-prediction units 244 (encoder)and 344 (decoder) may not be available in case the picture processingcoding is limited to a single picture 17. All other functionalities(also referred to as tools or technologies) of the video encoder 20 andvideo decoder 30 may equally be used for still picture processing, e.g.residual calculation 204/304, transform 206, quantization 208, inversequantization 210/310, (inverse) transform 212/312, partitioning 262/362,intra-prediction 254/354, and/or loop filtering 220, 320, and entropycoding 270 and entropy decoding 304.

Embodiments, e.g. of the encoder 20 and the decoder 30, and functionsdescribed herein, e.g. with reference to the encoder 20 and the decoder30, may be implemented in hardware, software, firmware, or anycombination thereof. If implemented in software, the functions may bestored on a computer-readable medium or transmitted over communicationmedia as one or more instructions or code and executed by ahardware-based processing unit. Computer-readable media may includecomputer-readable storage media, which corresponds to a tangible mediumsuch as data storage media, or communication media including any mediumthat facilitates transfer of a computer program from one place toanother, e.g., according to a communication protocol. In this manner,computer-readable media generally may correspond to (1) tangiblecomputer-readable storage media which is non-transitory or (2) acommunication medium such as a signal or carrier wave. Data storagemedia may be any available media that can be accessed by one or morecomputers or one or more processors to retrieve instructions, codeand/or data structures for implementation of the techniques described inthis disclosure. A computer program product may include acomputer-readable medium.

By way of example, and not limiting, such computer-readable storagemedia can comprise RAM, ROM, electrically erasable programmable ROM(EEPROM), compact-disc (CD-ROM) or other optical disk storage, magneticdisk storage, or other magnetic storage devices, flash memory, or anyother medium that can be used to store desired program code in the formof instructions or data structures and that can be accessed by acomputer. Also, any connection is properly termed a computer-readablemedium. For example, if instructions are transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.It should be understood, however, that computer-readable storage mediaand data storage media do not include connections, carrier waves,signals, or other transitory media, but are instead directed tonon-transitory, tangible storage media. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, DVD, floppy diskand BLU-RAY DISC, where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers. Combinations of the aboveshould also be included within the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one ormore DSPs, general purpose microprocessors, ASICs, FPGAs, or otherequivalent integrated or discrete logic circuitry. Accordingly, the term“processor,” as used herein may refer to any of the foregoing structureor any other structure suitable for implementation of the techniquesdescribed herein. In addition, in some aspects, the functionalitydescribed herein may be provided within dedicated hardware and/orsoftware modules configured for encoding and decoding, or incorporatedin a combined codec. Also, the techniques could be fully implemented inone or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a wireless handset, an integratedcircuit (IC) or a set of ICs (e.g., a chip set). Various components,modules, or units are described in this disclosure to emphasizefunctional aspects of devices configured to perform the disclosedtechniques, but do not necessarily require realization by differenthardware units. Rather, as described above, various units may becombined in a codec hardware unit or provided by a collection ofinteroperative hardware units, including one or more processors asdescribed above, in conjunction with suitable software and/or firmware.

What is claimed is:
 1. A method comprising: obtaining first referencesamples of a current block from available top reference samples (Top[i])in reference lines of the current block, wherein i=0 . . . W, andwherein W represents a width of the current block; obtaining thirdreference samples of a reference block, wherein at least one of thethird reference samples is based on an integer part of a fractionalmotion vector (MV), and wherein at least one of the third referencesamples is obtained using one of:(Imvx=(mvx>>mvp)<<mvp,Imvy=(mvy>>mvp)<<mvp); or(Imvx=(mvx>>mvp)<<mvp,Imvy=mvy); or(Imvx=mvx,Imvy=(mvy>>mvp)<<mvp), wherein (Imvx, Imvy) represents an MVof one of the third reference samples, wherein (mvx, mvy) is thefractional MV, and wherein mvp is a constant; estimating localillumination compensation (LIC) parameters using the first referencesamples and the third reference samples; and obtaining inter predictionof the current block according to the LIC parameters.
 2. The method ofclaim 1, further comprising further obtaining the first referencesamples from available fourth reference samples (Left[j]) in thereference lines, wherein Left[j] represents available left referencesamples of the current block, wherein j=0 . . . H, and wherein Hrepresents a height of the current block.
 3. The method of claim 2,further comprising applying at least one of the top reference samples orthe available left reference samples for the LIC parameters.
 4. Themethod of claim 1, further comprising performing motion compensation(MC) in parallel with estimating the LIC parameters.
 5. The method ofclaim 1, further comprising further estimating the LIC parameters usinga linear approximation.
 6. The method of claim 1, wherein the firstreference samples and the third reference samples are unfilteredreference samples.
 7. The method of claim 1, wherein at least one of thethird reference samples is based on co-located samples from thereference block based on the integer part of the fractional MV.
 8. Acoding apparatus comprising: a memory configured to store instructions;and a processor coupled to the memory and configured to execute theinstructions that cause the coding apparatus to be configured to: obtainfirst reference samples of a reference block, wherein at least one ofthe first reference samples is based on an integer part of a fractionalmotion vector (MV), and wherein at least one of the third referencesamples is obtained using one of:(Imvx=(mvx>>mvp)<<mvp,Imvy=(mvy>>mvp)<<mvp);(Imvx=(mvx>>mvp)<<mvp,Imvy=mvy); or(Imvx=mvx,Imvy=(mvy>>mvp)<<mvp), wherein (Imvx, Imvy) represents an MVof one of the third reference samples, wherein (mvx, mvy) is thefractional MV, and wherein mvp is a constant; obtain second referencesamples of a current block from available top reference samples (Top[i])in reference lines, wherein i=0 . . . W, and wherein W represents awidth of the current block; estimate local illumination compensation(LIC) parameters using the second reference samples and the firstreference samples; and obtain inter prediction of the current blockaccording to the LIC parameters.
 9. The coding apparatus of claim 8,wherein the instructions further cause the coding apparatus to beconfigured to further obtain the second reference samples from availablefourth reference samples (Left[j]) in the reference lines, whereinLeft[j] represents available left reference samples of the currentblock, wherein j=0 . . . H, and wherein H represents a height of thecurrent block.
 10. The coding apparatus of claim 9, wherein theinstructions further cause the coding apparatus to be configured toapply at least one of the top reference samples or the available leftreference samples for the LIC parameters.
 11. The coding apparatus ofclaim 8, wherein the instructions further cause the coding apparatus tobe configured to perform motion compensation (MC) in parallel withestimating the LIC parameters.
 12. The coding apparatus of claim 8,wherein the instructions further cause the coding apparatus to beconfigured to further estimate the LIC parameters using a linearapproximation.
 13. The coding apparatus of claim 8, wherein the firstreference samples and the third reference samples are unfilteredreference samples.
 14. The coding apparatus of claim 8, wherein at leastone of the third reference samples is based on co-located samples fromthe reference block based on the integer part of the fractional MV. 15.A computer program product comprising computer-executable instructionsstored on a non-transitory computer-readable recording medium that, whenexecuted by a processor, cause an apparatus to: obtain first referencesamples of a current block from available top reference samples (Top[i])in reference lines, wherein i=0 . . . W, and wherein W represents awidth of the current block; obtain third reference samples of areference block, wherein at least one of the third reference samples isbased on an integer part of a fractional motion vector (MV), and whereinat least one of the third reference samples is obtained using one of:(Imvx=(mvx>>mvp)<<mvp,Imvy=(mvy>>mvp)<<mvp); or(Imvx=(mvx>>mvp)<<mvp,Imvy=mvy); or(Imvx=mvx,Imvy=(mvy>>mvp)<<mvp), wherein (Imvx, Imvy) represents an MVof one of the third reference samples, wherein (mvx, mvy) is thefractional MV, and wherein mvp is a constant; estimate localillumination compensation (LIC) parameters using the first referencesamples and the third reference samples; and obtain inter prediction ofthe current block according to the LIC parameters.
 16. The computerprogram product of claim 15, wherein the computer-executableinstructions further cause the apparatus to further obtain the availablefourth reference samples (Left[j]) in the reference lines, whereinLeft[j] represents available left reference samples of the currentblock, wherein j=0 . . . H, and wherein H represents a height of thecurrent block.
 17. The computer program product of claim 16, wherein thecomputer-executable instructions further cause the apparatus to apply atleast one of the top reference samples or the available left referencesamples for the LIC parameters.
 18. The computer program product ofclaim 15, wherein the computer-executable instructions further cause theapparatus to perform motion compensation (MC) in parallel withestimating the LIC parameters.
 19. The computer program product of claim15, wherein the first reference samples and the third reference samplesare unfiltered reference samples.
 20. The computer program product ofclaim 15, wherein at least one of the third reference samples is basedon co-located samples from the reference block based on the integer partof the fractional MV.